1. Field of the Invention
This method relates generally to seismic data processing, and more particularly to a method for evaluating and suppressing anomalous noise amplitudes in seismic data.
2. Discussion of the Related Art
Amplitudes of seismic records have been thoroughly investigated over the last several decades. Gutenberg (1936), referring to earlier works of Knott (1899) and Zoepprits et al. (1912), discussed the expected amplitudes of seismic reflections from the subsurface. After the introduction of automatic gain control (AGC) instrumentation and recording devices, geophysical interpretation was directed more toward the study of time anomalies and reflection character. The study of reflection amplitudes did not become popular again until the development of binary gain and floating point recording. These developments led to the "bright spot" interpretation technique, which incorporated the study of amplitude anomalies into seismic interpretation. The acceptance of the "bright spot" technique was industry wide.
The first application of the technique was to offshore seismic data, principally in deltaic regions. It quickly became evident that the brightness or dullness of the reflection was of significance when making interpretation. Hermont (1969), O'Doherty and Anstey (1971), and Larner et al. (1973) demonstrated the significance and diagnostic value of reflection amplitudes.
Application of these techniques to land situations required a more intensive study of the factors which affect recorded amplitudes. Sheriff (1973), Taner and Koehler (1974) provided an review of these factors, while Houba et al. (1973) and Disher and Randle (1973) discussed a processing method for land data. It is generally recognized that several factors play a role in the amplitude of the received seismic signal. Larner et al. (1973), Larner (1975), and Taner and Koehler (1981) as well as others determined several surface and subsurface characteristics which affect the amplitude of the received seismic signals. The assignee of this invention, as early as October 1977, developed a computation for correcting or removing anomalous noise amplitudes from seismic data. Taner and Koehler (1981) show an example of a similar computation which attempts to recognize anomalous amplitudes caused by outside disturbances such as near-subsurface layers (weathered zone) which might distort or influence the behavior of the received seismic signals.
Of all of the above individuals who studied anomalous amplitude problems in seismic data processing, not one considered noise in any of the calculations/corrections.